Rear optical device, assembly forming a modular zoom, and method for changing the zoom of a camera lens

Abstract

Disclosed is a rear optical device (14A, 14B) intended to form an image depending on an optical flux captured by a front optical device (12), the rear optical device (14A, 14B) comprising - a housing (22A, 22B) comprising a sensor (26A, 26B) defining an image format, and - a coupling unit (24A, 24B) intended to removably couple the housing (22A, 22B) to a front optical device (12) to form a zoom (18A, 18B), the coupling unit (24A, 24B) being formed of a nut (30A, 30B).

Description

[0001] DESCRIPTION

[0002] TITLE: Rear optical device, modular zoom forming assembly and method for changing the zoom of a shooting lens

[0003] The present invention relates to a rear optical device for forming an image based on an optical flow captured by a front device, a modular zoom forming assembly and a method for changing the zoom of a shooting lens.

[0004] Typically, a cinematographic zoom lens is tailored for use with a specific sensor size, so as to deliver an image in a given format.

[0005] It is possible to install accessories, such as converters, to adapt the zoom to form an image of another format.

[0006] However, the use of such converters leads to a significant loss of quality and also an increase in space requirements.

[0007] In order to overcome these drawbacks, it is known, in particular from document FR3060771A1, to use a modular optical system comprising a front optical device capable of capturing an optical flow and a plurality of rear optical devices, each intended to form an image as a function of an optical flow captured by the front optical device in a given format. The coupling of the common front device and a rear optical device forms a zoom adapted to a specific image format.

[0008] Each rear optical device consists of many sub-elements, such as the housing including the image format-specific sensor, the iris diaphragm, the indexing ring, the focal engraving ring and the focusing ring.

[0009] However, changing a zoom lens from one format to another is relatively complex. For example, it is necessary to disassemble each sub-element forming the first rear optical device, then reassemble each sub-element forming the second rear optical device. These operations of disassembling and assembling the sub-elements must be carried out in a specific order and generally require many specific tools.

[0010] These operations are therefore generally tedious and must be carried out in a dedicated service center.

[0011] One of the aims of the invention is to improve this solution and to propose an optical assembly making it possible to modify the image format simply, quickly and without specific tools, while maintaining good image quality. To this end, the invention proposes a rear optical device intended to form an image as a function of an optical flow captured by a front optical device, the rear optical device comprising:

[0012] - a housing comprising a sensor defining an image format, and

[0013] - a coupling unit for removably coupling the housing to a front optical device to form a zoom lens, the coupling unit being formed by a nut.

[0014] According to a particular implementation method, the nut is a notched nut.

[0015] The invention also relates to a modular zoom forming assembly comprising:

[0016] - a front optical device capable of capturing an optical flow,

[0017] - a first rear optical device as described above, the coupling by the nut of the first rear optical device and the front optical device forming a first zoom, and

[0018] - a second rear optical device as described above, the coupling by the nut of the second rear optical device and the front optical device forming a second zoom.

[0019] Depending on particular implementation methods, the set includes one or more of the following optional features, taken individually or in all technically possible combinations:

[0020] - the image format of the sensor of the first rear optical device is different from that of the second rear optical device;

[0021] - the front optical device comprises an iris diaphragm and an indexing ring suitable for adjusting the aperture of the diaphragm, the iris diaphragm and the indexing ring being common to the first zoom and the second zoom;

[0022] - in the first zoom, the diaphragm of the front optical device is at a first distance from the sensor of the first rear optical device, in the second zoom, the diaphragm of the front optical device is at a second distance from the sensor of the second rear optical device, the first distance and the second distance being substantially equal;

[0023] - the indexing ring is movable between a first configuration adapted for adjusting the aperture of the diaphragm of the first zoom and a second configuration adapted for adjusting the aperture of the diaphragm of the second zoom; and

[0024] - the front optical device comprises a focal engraving ring, the focal engraving ring being common to the first zoom and the second zoom, the focal engraving ring being movable between a first configuration adapted for adjusting the focal length of the first zoom and a second configuration adapted for adjusting the focal length of the second zoom.

[0025] The invention also relates to a method of changing the zoom of a shooting lens comprising the following steps:

[0026] - providing an assembly as described above, the front optical device being coupled to the first rear optical device so as to form the first zoom,

[0027] - rotating the nut of the first rear device so as to release the first rear optical device from the front optical device, and

[0028] - placing the second rear device on the front optical device and rotating the nut of the second rear optical device so as to couple the front optical device to the second rear optical device and form the second zoom.

[0029] According to a particular embodiment, the front optical device comprises an iris diaphragm and an indexing ring, the method comprising an additional step of rotating the indexing ring of the front optical device from a first configuration suitable for adjusting the aperture of the diaphragm of the first zoom to a second configuration suitable for adjusting the aperture of the diaphragm of the second zoom and / or the front optical device comprises a focal engraving ring, the method comprising an additional step of translating the focal engraving ring of the front optical device from a first configuration suitable for adjusting the focal length of the first zoom to a second configuration suitable for adjusting the focal length of the second zoom.

[0030] The invention and its advantages will be better understood upon reading the following description, given solely as a non-limiting example, and made with reference to the appended drawings, in which:

[0031] - [Fig 1] Figure 1 is a schematic representation of a modular zoom forming assembly according to the invention;

[0032] - [Fig 2] Figure 2 is a schematic representation of a first zoom formed by the whole of Figure 1; and

[0033] - [Fig 3] Figure 3 is a schematic representation of a second zoom formed by the whole of Figure 1.

[0034] Figure 1 illustrates a set 10 for forming a modular zoom, and in particular a cinematographic shooting lens zoom.

[0035] The assembly 10 comprises a front optical device 12 capable of capturing an optical flow, a first rear optical device 14A and a second rear optical device 14B. The assembly 10 forms a first zoom 18A illustrated in Figure 2 by the coupling of the front optical device 12 and the first rear device 14A.

[0036] In the first zoom 18A, the first rear device 14A is arranged for example in the continuity of the front optical device 12 along a longitudinal axis X-X' (corresponding to the optical axis).

[0037] The first 18A zoom lens is, for example, suitable for providing an image in a first image format. The first image format is, for example, the FF format (which is the English abbreviation for "Full Frame").

[0038] The assembly 10 further forms a second zoom 18B illustrated in Figure 3 by the coupling of the front optical device 12 and the second rear device 14B.

[0039] In the second zoom 18B, the second rear device 14B is arranged for example in the continuity of the front optical device 12 along the longitudinal axis X-X'.

[0040] The second 18B zoom is suitable, for example, for providing an image in a second image format.

[0041] The second image format is preferably different from the first image format. The second image format is, for example, the S35 image format.

[0042] Alternatively, the first image format and the second image format are for example chosen from the S35 image format corresponding to a sensor size of 24.89x18.6 mm 2 , the FF image format corresponding to a sensor size of 24x36mm 2 and the 35mm academic format corresponding to a sensor size of 22x316mm 2 .

[0043] We first begin by describing more specifically the first rear optical device 14A and the second rear optical device 14B.

[0044] Each of the first rear optical device 14A and the second rear optical device 14B is intended to form an image resulting from an optical flow captured by the front optical device 12.

[0045] More particularly, the first rear optical device 14A is intended to form an image in the first image format, for example the FF format. The second rear optical device 14B is intended to form an image in the second image format, for example the S35 image format.

[0046] Each of the first rear optical device 14A and the second rear optical device 14B comprises a housing 22A, 22B and a coupling unit 24A, 24B.

[0047] The housing 22A, 22B of each of the first rear optical device 14A and the second rear optical device 14B comprises for example an outer wall 21A, 21B advantageously defining a housing 23A, 23B, preferably of revolution shape around the longitudinal axis X-X'. The housing 22A, 22B of each of the first rear optical device 14A and the second rear optical device 14B comprises a sensor 26A, 26B defining an image format.

[0048] Each sensor 26A, 26B is preferably housed in the corresponding housing 23A, 23B, for example at a longitudinal end of the housing 22A, 22B.

[0049] More particularly, each sensor 26A, 26B is a digital sensor of substantially rectangular shape. The size of the sensor 26A, 26B defines, for example, the corresponding image format.

[0050] For example, the image format of the sensor 26A of the first rear optical device 14A is different from that of the second rear optical device 14B.

[0051] In particular, the sensor 26A of the first rear optical device 14A defines the first image format.

[0052] In the case where the first image format is the FF format, the sensor 26A of the first rear optical device 14A has, for example, a rectangular shape with a length equal to 36 mm and a width equal to 24 mm.

[0053] In particular, the sensor 26B of the second rear optical device 14B defines the second image format.

[0054] In the case where the second image format is the S35 format, the sensor 26B of the second rear optical device 14B has, for example, a rectangular shape with a length equal to 24.89 mm and a width equal to 18.6 mm.

[0055] The housing 22A, 22B of each of the first rear optical device 14A and the second rear optical device 14B advantageously also comprises optical elements 28A, 28B, in particular fixed lenses housed in the corresponding housing 23A, 23B.

[0056] The coupling unit 24A, 24B of each of the first rear optical device 14A and the second rear optical device 14B is intended to removably couple said housing 22A, 22B to the front optical device 12 to form a zoom 18A, 18B.

[0057] More particularly, the coupling unit 24A of the first rear optical device 14A is intended to removably couple the housing 22A of the first rear optical device 14A to the front optical device 12 to form the first zoom 18A illustrated in Figure 2.

[0058] Likewise, the coupling unit 24B of the second rear optical device 14B is for removably coupling the housing 22B of the second rear optical device 14B to the front optical device 12 to form the second zoom lens 18B shown in Figure 3. The coupling unit 24A, 24B of each of the first rear optical device 14A and the second rear optical device 14B is formed of a nut 30A, 30B.

[0059] Advantageously, the coupling unit 24A, 24B of each of the first rear optical device 14A and the second rear optical device 14B comprises only said nut 30A, 30B.

[0060] More particularly, the coupling unit 24A, 24B of each of the first rear optical device 14A and the second rear optical device 14B does not include screws. The coupling is therefore performed without screws.

[0061] As illustrated in the figures, each nut 30A, 30B extends for example around a portion of the outer wall 21A, 21B of the corresponding housing 22A, 22B.

[0062] Preferably, each nut 30A, 30B is rotatable around said outer wall 21A, 21B of the housing 22A, 22B, for example between a locking position and a free position.

[0063] Advantageously, each nut 30A, 30B is a notched nut.

[0064] In other words, each nut 30A, 30B comprises an outer face having an alternation of notches and notches, so as to facilitate the gripping and rotation of the nut 30A, 30B.

[0065] We will now describe more specifically the front optical device 12 and its interactions with each of the first rear optical device 14A and the second rear optical device 14B.

[0066] The front optical device 12 comprises, for example, a housing 34 comprising an outer wall 36 delimiting a housing 38, in particular of a shape of revolution around the longitudinal axis X-X'.

[0067] The front optical device 12 preferably comprises at least one coupling element 40 capable of cooperating with the nut 30A, 30B of each of the first rear optical device 14A and the second rear optical device 14B.

[0068] The coupling element 40 is for example provided on the outer wall 36 of the housing 34.

[0069] In particular, the coupling by the nut 30A of the first rear optical device 14A and the front optical device 12 forms the first zoom 18A.

[0070] More specifically, the coupling element 40 of the front optical device 12 cooperates, for example by form cooperation, with the nut 30A of the first rear optical device 14A in its locking position in order to fix the housing 22A of the first rear optical device 14A on the front optical device 12 and form the first zoom 18A as illustrated in Figure 2. Similarly, the coupling by the nut 30B of the second rear optical device 14B and the front optical device 12 forms the second zoom 18B.

[0071] More specifically, the coupling element 40 of the front optical device 12 cooperates, for example by form cooperation, with the nut 30B of the second rear optical device 14B in its locking position in order to fix the housing 22B of the second rear optical device 14B on the front optical device 12 and form the second zoom 18B as illustrated in Figure 3.

[0072] The front optical device 12 preferably comprises optical elements (not shown) capable of capturing an optical flow, such as for example at least one group of movable lenses housed in the housing 38.

[0073] Advantageously, the front optical device 12 comprises an iris diaphragm 42 and an indexing ring 44 suitable for adjusting the opening of the diaphragm 42.

[0074] Preferably, as can be seen in the figures, the iris diaphragm 42 and the indexing ring 44 are common to the first zoom 18A and the second zoom 18B.

[0075] In particular, in the first zoom 18A illustrated in Figure 2, the diaphragm 42 of the front optical device 12 is at a first distance D A of the sensor 26A of the first rear optical device 14A. The first distance D A is preferably measured along the longitudinal axis X-X'.

[0076] Similarly, in the second zoom 18B illustrated in Figure 3, the diaphragm 42 of the front optical device 12 is at a second distance D B of the sensor 26B of the second rear optical device 14B. The second distance D B is preferably measured along the longitudinal axis X-X'.

[0077] Advantageously, the first distance D A and the second distance D B are substantially equal, so that the size of the first zoom 18A and the second zoom 18B is substantially identical.

[0078] In other words, the difference between the first distance D A and the second distance D B is preferably less than 0.05 mm.

[0079] For this purpose, the optical elements 28A, 28B of each of the first rear optical device 14A and the second rear optical device 14B have been advantageously configured so as to allow this equality between the first distance D Aand the second distance D B .

[0080] Preferably, the indexing ring 44 is movable between a first configuration illustrated in Figure 2 and a second configuration illustrated in Figures 1 and 3.

[0081] For example, the indexing ring 44 is rotatable about the longitudinal axis X-X' relative to the housing 34, for example by a rotation of 180° between the first configuration and the second configuration. In its first configuration illustrated in Figure 2, the indexing ring 44 is adapted for adjusting the aperture of the diaphragm 42 of the first zoom 18A.

[0082] In particular, in its first configuration, the indexing ring 44 makes visible first indexing engravings 46 specific to the first image format.

[0083] Each first indexing engraving 46 defines for example a specific opening of the diaphragm 42 adapted to the first image format defined by the first zoom 18A, and in particular adapted to the size of the sensor 26A of the first rear optical device 14A.

[0084] For example, the indexing ring 44 includes a first window 48 making the first indexing engravings 46 visible only in the first configuration of the indexing ring 44.

[0085] In its second configuration illustrated in Figure 3, the indexing ring 44 is adapted for adjusting the aperture of the diaphragm 42 of the second zoom 18B.

[0086] In particular, in its second configuration, the indexing ring 44 makes visible second indexing engravings 50 specific to the second image format. Each second indexing engraving 50 defines for example a specific opening of the diaphragm 42 adapted to the second image format defined by the second zoom 18B, and in particular adapted to the size of the sensor 26B of the second rear optical device 14B.

[0087] For example, the index ring 44 includes a second window 52 making the second index engravings 50 visible only in the second configuration of the index ring 44.

[0088] Advantageously, the front optical device 12 further comprises a focal engraving ring 54.

[0089] Preferably, as can be seen in the figures, the focal engraving ring 54 is common to the first zoom 18A and to the second zoom 18B.

[0090] Preferably, the focal engraving ring 54 is movable between a first configuration illustrated in Figure 2 and a second configuration illustrated in Figure 3.

[0091] For example, the focal engraving ring 54 is movable in translation along the longitudinal axis X-X' relative to the housing 34 between its first configuration and its second configuration.

[0092] In its first configuration illustrated in Figure 2, the focal engraving ring 54 is adapted for adjusting the focal length of the first zoom 18A.

[0093] In its second configuration illustrated in Figure 3, the focal engraving ring 54 is adapted for adjusting the focal length of the second zoom 18B.

[0094] Advantageously, the front optical device 12 also comprises a focusing ring 56. Preferably, the focusing ring 56 is common to the first zoom 18A and to the second zoom 18B.

[0095] In particular, in one example, the focusing ring 56 comprises a single configuration. The focusing ring 56 advantageously does not need to be adapted when changing between the first zoom 18A and the second zoom 18B, in particular in the case where the first distance D A and the second distance D B are equal.

[0096] A method of changing the zoom of a shooting lens will now be described.

[0097] The method comprises a first step of providing the assembly 10 for forming a modular zoom.

[0098] In particular the method of changing from the first zoom 18A illustrated in Figure 2 to the second zoom 18B illustrated in Figure 3 will be described.

[0099] Thus, during this first step, the front optical device 12 is coupled to the first rear optical device 14A so as to form the first zoom 18A.

[0100] The method then comprises a step of rotating the nut 30A of the first rear device 14A so as to release the first rear optical device 14A from the front optical device 12.

[0101] In particular, the nut 30A of the first rear device 14A is turned from its locking position to its free position.

[0102] Advantageously, this step of rotating the nut 30A is the only step necessary to release the first rear optical device 14A from the front optical device 12.

[0103] In particular, it is not necessary to unscrew any screws to release the first rear optical device 14A from the front optical device 12.

[0104] The first rear optical device 14A is then preferably placed away from the front optical device 12.

[0105] The method is followed by a step of placing the second rear device 14B on the front optical device 12.

[0106] The method then comprises a step of rotating the nut 30B of the second rear device 14B so as to couple the front optical device 12 to the second rear device 14B and form the second zoom 18B.

[0107] In particular, the nut 30B of the second rear device 14B is turned from its free position to its locking position.

[0108] Advantageously, this step of rotating the nut 30B is the only step necessary for coupling the second rear optical device 14B and the front optical device 12. In particular, it is not necessary to screw in any screws to couple the second rear optical device 14B and the front optical device 12.

[0109] Preferably, the method comprises an additional step of rotating the indexing ring 44 of the front optical device 12 from its first configuration adapted for adjusting the aperture of the diaphragm 42 of the first zoom 18A to its second configuration adapted for adjusting the aperture of the diaphragm 42 of the second zoom 18B.

[0110] In particular, the indexing ring 44 is for example rotated relative to the housing 34 by an angle of 180° around the longitudinal axis X-X', so that its second window 52 makes the second indexing engravings 50 visible.

[0111] Preferably, the method also comprises an additional step of translating the focal engraving ring 54 of the front optical device 12 from its first configuration adapted for adjusting the focal length of the first zoom 18A to its second configuration adapted for adjusting the focal length of the second zoom 18B.

[0112] In particular, the focal engraving ring 54 is moved relative to the housing 34 along the longitudinal axis X-X', for example forward.

[0113] Advantageously, the process steps described above are the only steps necessary to change from the first zoom 18A to the second zoom 18B.

[0114] The assembly 10 for forming a modular zoom according to the invention is particularly advantageous, in particular thanks to the nut 30A, 30B of each of the rear devices 14A, 14B.

[0115] In fact, the nut 30A, 30B makes it possible to couple or release with a single rotation step each of the rear devices 14A, 14B from the front device 12.

[0116] Furthermore, changing between the first zoom 18A and the second zoom 18B, and thus changing the image format, requires only a small number of steps. Changing the image format is therefore quick and straightforward. In particular, it can be carried out without special tools, for example outside a service center.

[0117] Those skilled in the art will understand that the embodiments and variants previously described can be combined with each other provided that they are technically compatible.

Claims

CLAIMS 1. A rear optical device (14A, 14B) for forming an image based on an optical flow captured by a front optical device (12), the rear optical device (14A, 14B) comprising: a housing (22A, 22B) comprising a sensor (26A, 26B) defining an image format, and a coupling unit (24A, 24B) for removably coupling the housing (22A, 22B) to a front optical device (12) to form a zoom (18A, 18B), the coupling unit (24A, 24B) being formed of a nut (30A, 30B).

2. Rear optical device (14A, 14B) according to claim 1, wherein the nut (30A, 30B) is a notched nut.

3. Set (10) for forming a modular zoom comprising: - a front optical device (12) capable of capturing an optical flow, - a first rear optical device (14A) according to claim 1 or 2, the coupling by the nut (30A) of the first rear optical device (14A) and the front optical device (12) forming a first zoom (18A), and - a second rear optical device (14B) according to claim 1 or 2, the coupling by the nut (30B) of the second rear optical device (14B) and the front optical device (12) forming a second zoom (18B).

4. Assembly (10) according to claim 3, in which the image format of the sensor (26A) of the first rear optical device (14A) is different from that of the second rear optical device (14B).

5. Assembly (10) according to any one of claims 3 or 4, wherein the front optical device (12) comprises an iris diaphragm (42) and an indexing ring (44) suitable for adjusting the opening of the diaphragm (42), the iris diaphragm (42) and the indexing ring (44) being common to the first zoom (18A) and to the second zoom (18B).

6. Assembly (10) according to claim 5, wherein in the first zoom (18A), the diaphragm (42) of the front optical device (12) is at a first distance (D A ) of the sensor (26A) of the first rear optical device (14A), in the second zoom (18B), the diaphragm (42) of the front optical device (12) is at a second distance (D B ) of the sensor (26B) of the second rear optical device (14B), the first distance (D A ) and the second distance (D B ) being substantially equal.

7. Assembly (10) according to claim 5 or 6, wherein the indexing ring (44) is movable between a first configuration adapted for adjusting the aperture of the diaphragm (42) of the first zoom (18A) and a second configuration adapted for adjusting the aperture of the diaphragm (42) of the second zoom (18B).

8. An assembly (10) according to any one of claims 5 to 7, wherein the front optical device (12) comprises a focal engraving ring (54), the focal engraving ring (54) being common to the first zoom (18A) and to the second zoom (18B), the focal engraving ring (54) being movable between a first configuration adapted for adjusting the focal length of the first zoom (18A) and a second configuration adapted for adjusting the focal length of the second zoom (18B).

9. A method of changing the zoom of a shooting lens comprising the following steps: providing an assembly (10) according to any one of claims 4 to 8, the front optical device (12) being coupled to the first rear optical device (14A) so as to form the first zoom (18A), rotating the nut (30A) of the first rear device (14A) so as to release the first rear optical device (18A) from the front optical device (12), and - placing the second rear device (14B) on the front optical device (12) and rotating the nut (30B) of the second rear optical device (14B) so as to couple the front optical device (12) to the second rear optical device (14B) and form the second zoom (18B).

10. A method of changing according to claim 9, wherein the front optical device (12) comprises an iris diaphragm (42) and an indexing ring (44), the method comprising a further step of rotating the indexing ring (44) of the front optical device (12) from a first configuration adapted for adjusting the aperture of the diaphragm (42) of the first zoom (18A) to a second configuration adapted for adjusting the aperture of the diaphragm (42) of the second zoom (18B); and / or the front optical device (12) comprises a focal engraving ring (54), the method comprising a further step of translating the focal engraving ring (54) of the front optical device (12) of a first configuration adapted for adjusting the focal length of the first zoom (18A) to a second configuration adapted for adjusting the focal length of the second zoom (1 SB).

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